Trimethylgallium, often abbreviated to TMG or TMGa, is the organogallium compound with the formula Ga(CH3)3.

[2] When examined in detail, the monomeric units are clearly linked by multiple weak Ga---C interactions, reminiscent of the situation for trimethylindium.

As noted by TMG discoverers Kraus and Toonder in 1933, the ether ligand is not readily lost, although it may be displaced with liquid ammonia.

TMG is the preferred metalorganic source of gallium for metalorganic vapour phase epitaxy (MOVPE) of gallium-containing compound semiconductors, such as GaAs, GaN, GaP, GaSb, InGaAs, InGaN, AlGaInP, InGaP, AlInGaNP and Ga2O3.

[6] These material are used in the production of LED lighting and semiconductors as a metalorganic chemical vapor deposition precursor.